Manufacture of sulfate of potash and alumina.



UNITED STATES PATENT o FroE;

HOWARD r. CHAZPPELL, or NEW YORK, N. Y.

MANUFACTURE OF SULFATE 0F POTASH A ND'ALUMINA.

No Drawing.

To all whom it may concern:

Be it known that I, HoWARD F. CHAP- PELL, a citizen of the UnitedStates, residing in the borough of Manhattan, in' the city, county, andState of New York, have invented certain new and useful Improvements inManufacture of Sulfate of Potash and Alumina; and I do hereby declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

This invention relates to the manufacture of sulfate of potassium and hih-grade oxid of aluminum, from natural eposits variously known as alumstone, alum rock and alunite. p

The practice of the invention involves a calcining operation designed toconvert the alkali compounds contained in the alunite into sulfatessoluble in water, and the aluminum compounds contained in the aluniteinto aluminum oxid insoluble in water.

' The soluble sulfates are then dissolved out of the calcined ore withwater, by any ordinary m ethod of leaching, thereby leaving the aluminumoxid. The soluble sulfates are recovered from the leachings.

The invention is of particular industrial .importance for the economicalutilization of those alum stones and alum rock deposits diameterdownward.

The alum stone or alunite is-calcined in any suitable furnace ofordinary construction; a cupola kiln or shaft furnace, such as is usedfor calcining lime, is well adapted -to calcine alum stone where it isin lump form and does not fall to powder or decrepitate by the heat ofthe furnace. A rotating cylinder of similar construction to those usedin calcining limeand cement is especially adapted to the calcining ofalum stone when in the condition of granules or powder, and requiresless fuel than other Specification of Letters Patent.

I Patented Aug.12,1913.

Application filed ll'anuarj 13, 1912. Serial No. 671,086.

types of furnaces. A reverberatory furnace of ordinary construction or amuffle roaster supplied. internally with a current of air can be usedfor the purpose of calciningalum stone or alunite, but the fuel costwill be greater.

" It is very desirable to treat the alunite in asstrong a current of airas is permissible without too great an expenditure of fuel.

To this end, when the alunite is treated in l the kiln or shaft furnace,if oil is used as fuel, it is injected by steam into a suitablecombustion chamber wheerin the amount of air admitted may be regulatedto give thormental chamber, having air admission ports to'regulate theheat of'the products of com- 1 bustion; whereupon they pass into thebase of the cupola kiln through suitable ports or twyer openings andthen pass through the 7'0 ough combustion, and the products ofcombustion then pass into an adjacent supple charge. If bituminous coalis used for fuel,

supplementary air-ports are arranged between the fire-boxes and thekiln, or other methods are taken to insure' the complete combustion ofthe fuel gases and a suflicient air-supply, as a reducing flame is to beavoided. Under these conditions, in the oxidizing atmosphere incident tothe operation, I find that-the resultant alumina is rendered insolublein water, without any substantial production of potassium aluminate,atcalcining temperatures which may' be varied according to the analysisof the alum stone or alum rock treated (particularly with reference toits percentage of silica present) from'fi50" C. to 1000 G. and upward.That is to say, at these temperatures, substantially all of the aluminumcompounds in the alunitefappear in the calcined final product asinsoluble o-xid of aluminum, it being feasible to continue the calciningoperation until this result is effected, without producing any materialproportion of potassium aluminate, even when the calcining temperatureis in the higherrange of 1000 C. and beyond. Where the alum stone oralum rock contains as low a percentage of silica as one or two per cent,I find it suitable to employ a temperature of from 800 C. to 1000 C.,as, for instance, the temperature at which the usual diagonally slottedsaggar clay cones rated to indicate that temperature range (used inceramic ware kilns) begin to fuse at the exposed edges of the slot; and,in fact, I recommend this high range of temperature in calcining alunitewhatever the percentage of silica present. It is also my experience thatthe fines may be calcined to advantage at,

" a tendency to clog the furnace and otherwise interfere with theoperation of the process. On this account, the ore is introduced intothe calcining furnaces at the farthest end from the source of heat andis gradually moved toward the fuel end, and is thus gradually subjectedto a progressive increase of temperature until the heat is suflicient toconvert the potassium compounds and other alkali compounds contained inthe alunite into sulfates soluble in water, and to convert the aluminumcompounds of the alunite into aluminum oxid.

Having thus described my invention, what I claim is:

1. The process of obtaining aluminum oxid and sulfate of potassiumfromnatural deposits of alum stone, alum rock, and alunite, whichcomprises submitting the same to a temperature suflicient to convertsubstantially all of the potassium compounds contained therein intopotassium sulfate, and substantially all of the aluminum compounds intoinsoluble aluminum oxid and thereupon lixiviating out the potassiumsulfate; sub" stantially as described.

2. Theprocess of obtaining aluminum oXid and sulfate of potassium fromnatural deposits of alum stone, alum rock, and alunite, which comprisessubmitting the same to a temperature higher than 750 C. until thealuminum compounds present are converted into insoluble aluminum oxidand the potassium compounds present are converted into potassiumsulfate, and thereupon liXiviating out, the potassium sulfate;substantially as described.

\ 3. The process of obtaining aluminum oxid and sulfate of potassiumfrom natural deposits of alum stone, alum rock, and alunite,.whichcomprises submitting the same to a temperature of about 800-1000 (1.,until the aluminum compounds present are converted into insolublealuminum maid and the potassium compounds present are converted intopotassium sulfate, and thereupon lixiviating out the potassium sulfate;substantially as described. 1

In testimony whereof I affix my signa-- ture, in presence of twowitnesses.

HOWARD F. CHAPPELL. \Vitnesses LEoN WALTER RosEN'rHAL, MINERVA LoBEL,

